[Prior Art]
It has heretofore been known methods to treat the surface of a resin with a fluorine compound (oligomer) having fluoroalkyl groups at both ends of its molecule and a functional group joined to an intermediate chain thereof. Since the fluoroalkyl groups at both ends of the fluorine compound used in the surface treatment of the resin are joined to the intermediate chain through a covalent bond, the expected effects by the surface treatment, such as imparting of tack-free property, surface lubricity, water and oil repellency, anti-staining property, antibacterial property and physiological activity, can be exhibited over a long period of time.
As processes (production processes of a surface-treated resin article) for surface treatment of a resin with such a fluorine compound, the following processes (1) and (2) have been introduced.
(1) A process comprising dissolving the fluorine compound together with the resin in an organic solvent and then removing the organic solvent (Japanese Patent Application Laid-Open No. 246573/1999).
(2) A process comprising dissolving the fluorine compound in a photo-polymerizable monomer to prepare a photo-curable composition, coating the surface of the resin (plastic) with the composition and photo-curing a coating film formed (Japanese Patent Application Laid-Open No. 245419/1998).
[Problems to be Solved by the Invention]
It is thus desirable that such a fluorine compound can be applied to rubber articles; that is to say, the fluorine compound can be used to treat the surface of rubber (produce a surface-treated rubber article).
However, the above-described processes (1) and (2) are suitable for use as a treatment process (production process of a resin article) of “resin”, whereas any rubber article good in surface properties such as water and oil repellency and anti-staining property cannot be provided even when “rubber” is treated in accordance with these processes.
The present inventors have therefore attempted the following processes (3) to (5).
(3) A process comprising immersing a molding (rubber base) composed of uncrosslinked rubber in a solution of such a fluorine compound, drying the molding and then subjecting the molding to a heat treatment, thereby crosslinking the rubber and at the same time, forming a coating film (surface-treating layer) on the surface of the molding.
(4) A process comprising immersing a molding (rubber base) composed of crosslinked rubber in a solution of the fluorine compound, drying the molding and then subjecting the molding to a heat treatment, thereby forming a coating film (surface-treating layer) on the surface of the molding.
(5) A process comprising compounding and mixing the fluorine compound together with a crosslinking agent with uncrosslinked rubber to prepare a rubber composition and subjecting the rubber composition to molding.
In the processes (3) and (4), however, adhesion force of the coating film (surface-treating layer) formed to the molding (rubber base) is small, and so the coating film is easy to be separated. The processed are thus not practical. In addition, since the fluorine compound forming the coating film is easy to be dissolved in various solvents, the coating film is eroded by or dissolved in a solvent, when the solvent is brought into contact with the rubber article obtained by the process (3) or (4), so that the coating film is removed from the surface of the molding.
On the other hand, the fluorine compound separates out (blooms or bleeds) on the surface of the rubber molding obtained by the process (5), and so the fluorine atom derived from this compound has been able to be unevenly distributed (maldistribute) in the vicinity of the surface of the rubber molding.
When a solvent is brought into contact with the rubber molding obtained in the above-described manner, however, the fluorine compound separated out on the surface thereof is dissolved in the solvent, and the fluorine compound is run out from the surface. As a result, there arises a problem that the surface properties (for example, water and oil repellency and physiological activity) imparted to the molding by the fluorine compound are destroyed or extinguished.